Going on the basis that the customer just wants an answer, I usually don't bring this matter up, but PetahW is exactly right.

These grips are worth at least $250 and by altering them in any way, you just took a major loss in value.
The fact is, that today the grips you just bought are worth over twice what your Colt 357 probably cost when new.

Buy a good gunsmith's Magna-Tip screwdriver bit that fits the grip screw from Brownell's and remove the grips when cleaning.
This will also allow inspection of the frame and prevent rust starting under the grips.